Re: Logical IO
Date: Thu, 19 Nov 2009 08:22:48 -0800 (PST)
Message-ID: <658054.11563.qm_at_web80607.mail.mud.yahoo.com>
> I ever tried to trace such CR events as 10200, but found
> they did not log the reads on some special blocks, such
> as segment header.
You're right John. A recent discussion on another forum concluded that the only way to find the current mode read is either use event 10046 (when the blocks are not already cached) or check x$bh for increase in touch count (class 4 for segment header, verify with file and block number). There's no event to trace CU read.
In addition, it appears that since 9iR2, event 10046 or SQL trace counts current mode read into CR read statistics for a simple query. You can do a test or see "Followup April 26, 2005 - 8am Central time zone" of
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:865586003021
Only select for update or DML shows "db block gets" in sqlplus autotrace (or equivalent in 10046 trace summary). See the last paragraph of
http://yong321.freeshell.org/oranotes/SegmentHeaderCR.txt
Yong Huang
-- http://www.freelists.org/webpage/oracle-lReceived on Thu Nov 19 2009 - 10:22:48 CST